1. Field of the Invention
The present invention relates to an inner-rotor motor including an encoder.
2. Description of the Related Art
Inner-rotor motors have often been used as driving sources in office machines, such as copy machines and multifunctional devices, and household electrical appliances. Some of such motors include encoders, as described in JP-A 11-215775 and JP-A 2005-229698, for example.
In a motor disclosed in JP-A 11-215775, a slit disc of an encoder is arranged to project radially outward from a rotor yoke. This results in an increase in the radial dimension of the motor. In general, in the case of an encoder including a transmissive sensor, if an encoder disc including slits defined therein is moved in an axial direction, the disc and the sensor come into contact with each other, resulting in a damage of the disc. Moreover, it is necessary to insert the disc through a gap in the sensor for installation of the disc. This complicates an operation of assembling the motor.
In a brushless motor described in JP-A 2005-229698, a disc of an encoder is arranged inside a rotor yoke. This complicates assembling of the motor. Moreover, the motor has to have an increased axial dimension in order to secure a space for the disc.
As such, there has been a demand for a reduction in the axial dimension of the motor, an improvement in reliability of the encoder, or a reduction in the number of steps in assembling the motor.